Inflatable mattress



FIG. 1 is a perspective view of the inflatable mattress showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right side elevational view, the left side being a mirror image thereof;

FIG. 4 is a bottom plan view thereof; and

FIG. 5 is an end elevational view, the opposite end view being a mirror image thereof. 

The ornamental design for a inflatable mattress, as shown and described. 